Under the rules of the so-called Schengen Area, which covers all EU countries except Bulgaria, Cyprus, Ireland, Romania and the UK, people still have to carry some form of ID and national police can still do spot-checks, so long as the European Commission does not think they amount to systematic border control.

For their part, Dutch police regularly go on buses or trains crossing the Belgian and German borders to demand papers, in a practice which surprises some travellers who thought they were in a borderless zone. From last August, Dutch police also use military-grade surveillance cameras called @migo-boras to identify suspect cars.Their figures for 2012 show that they caught 1,733 “illegal migrants.”

They put 627 of them in detention centres and handed over 380 people to Belgian or German police. They escorted the others back to Belgium or Germany or gave them a limited time to leave the Netherlands. They caught another 2,409 people who were red-flagged in the Schengen IT system for infractions such as unpaid speeding fines (386 were arrested because they could not pay the fines on the spot).

In terms of more serious crime, they caught 121 people smuggling cash for purposes of money-laundering. They caught 325 people carrying drugs and 259 people with illegal weapons. They intercepted 419 people with fake travel documents, 141 people guilty of smuggling illegal migrants and another 110 people involved human trafficking, such as eastern European women to be made to work in sex clubs.

The figures were higher in 2010 (3,230 “illegal migrants,” 4,081 red-flagged travellers). The Dutch military police, which does the checks, said the difference is due to Dutch attempts to fall into line with Schengen limitations on controls and on new EU laws, such as the Return Directive.

EU rules also limit the use of @migo-boras cameras to six days or 90 hours per month. When asked by EUobserver if Dutch policemen are frustrated by the EU curbs on their work, police spokesman Dennis Muller said only: “We work within the boundaries of the laws handed down to us and we do not give our opinion on this.” For its part, the European Commission last year queried whether @migo-boras violates EU rules.

But following contacts with the Dutch interior ministry, it says that both the cameras and the spot-checks are in line with the Schengen code. “We consider that Dutch mobile surveillance (supported by @migo-boras) does not have an effect equivalent to border checks, as they are not systematic, but limited in time,” commission spokesman Michele Cercone told EUobserver.

When asked if he is concerned that Schengen freedoms help organised crime groups to operate in the zone, he said: “The creation of the Schengen area is one of the most tangible, popular and successful achievements of the EU.”He added: “Free movement is central to the success of the EU single market and an important factor for European [economic] growth.”